1. Field of the Invention
This invention pertains to filtration apparatus, and more particularly to water filtration apparatus.
2. Description of the Relevant Art
Activated carbon is a common filtration medium for the adsorption and removal of organic contaminants in the purification of drinking water, and also of air. The activated carbon is typically housed within a tubular vessel body, open at each end, which ends are closed by end caps. Plastic materials are typically used to form the vessel body and the end cap because of the beneficial properties of plastics, namely, strength, durability, resistance to corrosion, ease of molding, and low cost. Polyvinyl chloride (PVC) is a commonly used plastic material for water filtration apparatus. PVC components are typically adhered together with known PVC cements.
It has been determined that PVC cements release volatile organic chemicals (VOC) as the cement cures and bonds the two PVC surfaces together. Other common methods for bonding plastics together, such as epoxy cements, thermal welding, and glues containing methylene chloride, also release VOCs during the joining process. These VOCs are considered hazardous to human and animal health according to the United States Environmental Protection Agency (EPA). The VOCs released upon curing of the adhesives, particularly in the closed environment of the interior of a water filtration device, are adsorbed onto the activated carbon contained within the vessel body. These VOCs are released into the initial water supply that passes through the vessel body and contacts the activated carbon. Tests have shown that initial VOC levels in water leaving the activated carbon can exceed the EPA standards for drinking water. An alternative, non-toxic method and apparatus for securing the components of a water filtration device is therefore necessary. Pressure levels in the filtration apparatus can reach 100 psi, and safety concerns also require that the joining method and apparatus resist rupture with pressures reaching 300 psi.